To fully understand the field of public health, it is helpful to understand how it became a discipline. For thousands of years, populations have been concerned with sanitation, housing, the provision of safe, clean food and water, and the control and treatment of disease. Public health evolved to address these concerns. These issues continue to be important today, along with the many new topics constantly added to the field. Although it was not always identified as a separate discipline, we can see examples of public health concerns in the earliest civilizations. Figure 1.1 shows some of the major historical events in the development of public health over the centuries.

The great writers, philosophers, and physicians of ancient Greece tell us of the beginnings of public health. In “Airs, Waters and Places,” Hippocrates, the esteemed Greek physician, discussed the relationship between one’s environment and health. He considered climate, soil, water, nutrition, and lifestyle to be important predictors of health outcomes^[5]. In addition, he distinguished between endemic and epidemic diseases. Endemic diseases are those that occur at an expected rate in a population and epidemic diseases are those that occur at a rate higher than expected. These terms will be further defined and their importance to public health discussed in Chapter 4.

The Middle Ages began and ended with pandemics of bubonic plague: the Plague of Justinian in 543 and the Black Death in 1348. A pandemic is an epidemic, or unexpectedly large disease outbreak, that impacts the entire globe. The etiology, or cause, of bubonic plague was not understood during the Middle Ages, but poor living conditions were known to contribute to frequent epidemics. Today, we know bubonic plague is caused by infection with Yersinia pestis, a bacterium transmitted from rats to humans by the fleas that bite both. In the Middle Ages, overcrowded cities with unreliable municipal sanitation systems and close proximity of animals and humans allowed rat populations to flourish and bubonic plague to spread rapidly. Near the end of the Middle Ages, around 1200, European cities began passing laws to improve public health and combat epidemics. These measures included the establishment of slaughter-houses and the regulation of livestock possession^[6]. Both of these improvements decreased the chances of passing disease between people and their animals. The regulation of food at public markets improved during the Middle Ages as well, with specific guidelines for the length of time specific food products could be sold and dedicated areas for waste disposal. These regulations prevented foodborne illnesses associated with eating rotten or outdated food and also prevented pests, including rats, from scavenging near the markets^[6].

The Renaissance (late 1300s to early 1600s) brought great strides in scientific discovery, laying the groundwork for advances in public health. During the Renaissance, two theories on the origin of epidemics prevailed. The first, taken from Hippocrates, held that environmental factors dictated the potential for outbreaks and that an individual’s susceptibility determined whether he or she would fall ill. The opposing theory of contagion, championed by Giolamo Fracastoro (1478-1533), evolved into our present understanding of infection. Fracastoro believed microscopic agents were responsible for disease and that these agents could be transmitted by direct contact, through the air, or by intermediate fomites (inanimate objects such as doorknobs or drinking glasses that harbor infectious disease). He and his contemporaries did not imagine these infectious agents to be alive, however. It was not until Anton von Leeuwenhock (1632-1723) observed the first microscopic organisms that people believed this to be possible. Despite earlier conjecture by some leading scientists, the germ theory of disease did not truly take hold until the late nineteenth century^[6].

As France led the world into the Age of Enlightenment in the eighteenth century, public health began in earnest. A humanitarian spirit and the desire for equality led to a social understanding of health. Infant mortality (death during the first year of life) was high on the list of concerns and disparities. The public health movement involved concerned citizens lobbying their governments to regulate alcohol and to provide for the safe conditions and fair treatment of all infants and children, regardless of their social standing^[6]. Simultaneously, health education became popular, in line with the Enlightenment tenets of universal education and information dissemination. Despite earlier interest in the relationship of environment, social factors, and disease, it was in this era that health surveys were first employed^[6]. Occupational health received attention as well, and the health of members of the armed services, especially sailors, and of metal workers and miners received attention. Rosen lists the various occupational ailments described during this time, including “dermatoses of shoemakers and metal workers, grocer’s itch, eczema of washerwoman, and baker’s itch”^{[6, p. 118]}. John Howard (1726-1790) exposed the appalling conditions in which English prisoners lived, rousing public outcry that led to improved conditions. Mental illness, which carried a severe stigma and generally led to institutionalization, began to be viewed as a public health problem, especially after physicians demonstrated that a stable, nurturing environment produced better treatment results among the “insane” than restraints and physical punishment. Variolation (deliberate infection with smallpox), a common practice originating in China and spreading through the East over the centuries, became popular in the West in the 1700s. Although somewhat effective at preventing a serious case of disease, the practice of exposing susceptible people to smallpox could also induce severe forms of the disease and contributed to epidemics. In 1798, Edward Jenner (1749-1823) used naturally acquired and fairly benign cowpox to inoculate against smallpox. Within three years, more than one hundred thousand people were vaccinated in England alone. As early as 1800, publications heralded the impending eradication of smallpox, an event that would be officially achieved in 1980^[6].

As the Industrial Revolution (between 1700 and 1900) spread from England through Europe and eventually to the United States, the health of workers quickly deteriorated, and calls for improved public health measures followed. The industrialization process widened gaps in income, causing the number of individuals receiving financial assistance from local governments to increase beyond capacity. In 1834, Edwin Chadwick (1800-1890) led the development of England’s Poor Law Amendment Act, which withdrew government support from the able-bodied poor in an effort to encourage self-sufficiency. The only assistance offered was placement in workhouses. The administration of this system occurred at the national level, with a hierarchy of regional and local boards below. This market system mobilized the workforce, leading to a significant social change. Factories appeared, and the population moved toward industrial centers, creating crowded urban areas and work conditions ripe for the spread of disease. Little city planning occurred as builders rushed to provide enough housing for the influx of workers. Meanwhile, the wealthy, who could afford to travel, moved to suburban or rural areas vacated by the masses. Sanitation systems and public parks were not planned in most cities. Few toilets were available to city dwellers, and there was no infrastructure for garbage removal or sewage systems. In 1833, the passage of the Factory Act dealt with working conditions and the poor living conditions of those workers it sought to protect. Throughout the 1830s and 1840s, legislation regulating mines, factories, and child labor passed in England and Europe^[6].